BOYE, Mexico - Clementina Arellano grew up with her six brothers in a shack in this dusty Mexican hamlet. Now 42, she's raising her sons in a spacious, 10-room mansion with Roman-style pillars at the doorway and a garden full of flowers and singing birds.

How did she transform her fortunes so dramatically? By waiting tables and sweating in a furniture factory for about 10 years in Hickory, N.C., and sending home up to $500 a month.

A couple of doors down, Berta Olgin, lives under a leaky roof, with skinny sheep gnawing at sparse patches of grass in her yard. Her sons all decided to stay in Mexico to work as farmers or laborers, earning about $10 a day.

The two women are a vivid illustration of why so many Mexicans head north from this arid valley in central Mexico. Those who make it to the U.S. send dollars to carve out a Mexican dream between gnarled cacti and jagged rocks. Those who stay behind condemn another generation to a life deprived of material privileges.

This is the reason millions of men and women risk their lives crossing deserts and rivers to sneak into the United States, and keep at it even as lawmakers in Washington argue over a sweeping crackdown.

Olgin, 67, is growing old surrounded by family, a pleasure that may be denied to many whose children have left. But sometimes she regrets her own children didn't join the exodus.

"I see that some people around here have got money to burn," she said, looking enviously across a dirt street at a group of workmen finishing the home of a man working in Hickory.

Last year, Mexican migrants sent home a record $20 billion, making them Mexico's biggest foreign earner after oil, according Mexico's Central Bank. In the first four months of this year, the amount was $7 billion, a 25 percent increase over the same period last year.

Half of it flows into poor villages like Boye, a corn-growing community of 900 people founded by Otomi Indians long before Europeans came to the Americas.

The men and women of Boye began heading north around 1990, after farm prices slumped. The U.S. economy was soon to enter its longest peacetime boom, and over the next 15 years, Boye sent more than 300 people over the border, mainly to North Carolina, town officials say.

Their dollars are seen everywhere in sun-soaked Boye. The schoolhouse, village church and even the paved main streets were built with funds from "el Norte," sent by migrant clubs in the U.S. that collect donations from former residents.

The most startling spectacle is the houses. Families of migrants have ripped away their corrugated-iron shacks and built ostentatious brick homes over their ancestral plots of farm land.

Nicolas Sanchez, 34, proud owner of a gated residence on the edge of Boye, first trekked over the Sonora desert and headed to Hickory when he was 21. He labored by day in a furniture factory, starting at $6 an hour. At night, he worked at Taco Bell.

"It's hard when you arrive in a strange country and spend all your time working," Sanchez said in English, sitting with his young son in a Ford pickup truck. "You have to be strong and keep your eyes on the prize."

Sanchez wired back at least $500 a month to his parents, who collected it in pesos at a nearby town. They used about half for their living expenses and invested the rest in building a new family home.

With free land, a wealth of raw materials in the region and an abundance of cheap labor, the two-story house was built for a little over $10,000.

Alfredo Martinez, 41, headmaster of the village elementary school, says up to 80 percent of Boye's schoolchildren drop out to sneak over the border.

"We could do with doctors and professionals here. All we get is migrants and builders," Martinez complained, watching children sink basketballs on a dollar-funded stone court.

Very few villagers come back to start successful businesses, he said. In fact, many of Boye's young men and women settle down north of the border and never return, leaving the town dotted by half-finished skeletons of lavish homes.

Sanchez moved back to Boye and his new house last year, and has opened a boxing and karate club in a nearby town. But it doesn't earn much and he may return to the United States, especially if Congress agrees to allow more legal migration.

"I prefer it here. It's quiet and you can do whatever you want," he said, looking at the deserted village square. "But in the United States, if you work hard, they pay you well. All this problem with the border and the soldiers and the walls — It's all just about the dollars. It's all just business."